Method for mercerizing stretchable core spun yarns



United States Patent 3,549,310 METHOD FOR MERCERIZIN G STRETCHABLE CORESPUN YARNS Walter A. Gardner, 506 Piccadilly Circle, Gastonia, NC. 28052Continuation-impart of application Ser. No. 550,526, May 16, 1966. Thisapplication July 29, 1966, Ser. No. 568,791

Int. Cl. D06m 1/02; D02g 3/36 US. Cl. 8125 6 Claims ABSTRACT OF THEDISCLOSURE Core-spun yarns of stretchable core yarns and sheathes ofstable fibers are continuously drawn from yarn packages at a rate ofapproximately 150 to approximately 375 yards per minute by driven rolls.The continuously moving yarn is subjected to a drag working against thedriven rolls to tension the yarn and maintain the tension atapproximately 80 percent of that which the yarn is capable ofwithstanding without breaking. The continuously moving tensioned yarnpasses through a mercerizing solution and then a neutralizing solutionbefore being dried and packaged.

This application is a continuation-in-part of my copending application,Ser. No. 550,526, filed May 16, 1966, now abandoned.

The invention relates generally to methods and apparatus formanufacturing textiles, and particularly to a method and apparatus forcommercially mercerizing corespun yarns consisting of stretchable coreyarns and sheathes of staple fibers.

Mercerization is a finishing process extensively used on cotton yarn andcloth, essentially consisting of impregnating the material with a cold,strong sodium hydroxide solution. The treatment increases the strengthand affinity for dyes, and, most important, if done under tension, theluster is remarkably increased. Conventional apparatus used commerciallyfor warp mercerizing cotton yarn may handle approximately twenty-two ormore warps at a time. Since each warp consists of hundreds of ends ofyarn, it will be appreciated that commercial mercerization of cottonyarn is a large scale operation requiring very expensive apparatus.

In the use of conventional apparatus, the warps are passed through twosets of rolls. The second set is operated at a higher surface speed thanthe first set, in consequence of which the yarn therebetween istensioned. While thus tensioned, the yarn is impregnated with thetreatment solution. Due to the great number of yarns being processed,the pressure applied by the rolls to the yarns in order to develop thegrip necessary to prevent slippage of the yarns between the rolls isvery substantial. In fact it is so great that there is danger ofcrushing the yarns. In addition, since each warp contains the samenumber of yarns, and since the diameter of the yarns may vary from warpto warp, the size of the warps in transverse section may vary from warpto warp. Thus the grip of the rolls on the larger warps tends to befirmer than that on the smaller warps, as a consequence of which theremay be some slippage between the smaller warps and the rolls. This meansthat the tensioning effort applied to the larger warps will tend to begreater than that applied to the smaller warps, which may not bedesirable. Furthermore, some of the yarns in each warp will not comeinto contact with the rolls. Thus there will be slippage not onlybetween some of the warps and the rolls, but also between the individualyarns of each warp. This means that the tensioning etlort applied to theyarns that 3,549,310 Patented Dec. 22, 1970 ice come into contact withthe rolls will be greater than that applied to those that do not comeinto contact with the rolls, which may not be desirable. Due to thispossibility of slippage, tensioning the yarns by passing the warpsthrough two sets of rolls operating at dillerent surface speeds is notsatisfactory for all purposes.

For example, commercial core-spun yarns consisting of stretchable coreyarns and sheathes of staple fibers, are known, but such yarns are notmercerized because of the difiiculties experienced in tensioning theyarns properly when utilizing conventional apparatus. In order todevelop an acceptable luster, the yarns must be processed without beingcrushed, each yarn must be subjected to the same tension while passingthrough the treatment solution, and the tension must be a predeterminedhigh percentage of the maximum tension which the yarn is capable ofwithstanding without breaking. These desiderata cannot be realized whenconventional apparatus is utilized.

Another reason for not mercerizing core-spun yarns consisting ofstretchable core yarns and sheathes of staple fibers is that if thestretchable core is made of a material (for example, spandex) that willdeteriorate if overexposed to the mercerizing solution, excessive lossof yarn occurs when the apparatus is threaded up at the beginning of arun and when there is a breakdown in the operation. Normally, the yarnis not exposed to the mercerizing solution for more than about ninetyseconds. However, when threading up and when there is a breakdown,perhaps a yard or so of each yarn passing through the mercerizingsolution may be exposed thereto for more than the maximum safe period oftime, as a consequence of which a minimum of approximately 8000 yards ofyarn is lost. Needless to say, such a loss is prohibitive.

Mercerization of commercial core-spun yarns consisting of stretchablecore yarns and sheathes of staple fibers is important because withoutsuch yarns the manufacturer of mens half-hose, for example, has only achoice between several evils. He may use filamentary yarns, in whichcase his product will lack a good hand and luster. In addition, thesizes that must be stocked will be excessive. He may use conventionalspun yarns of staple fibers, in which case his product will have a goodhand and luster. However, the sizes that must be stocked will beexcessive. He may use core-spun yarns consisting of unstretchable coreyarns and sheathes of staple fibers, in which case his product will havea good hand, but, whether mercerized or not, will lack luster. Inaddition, the sizes that must be stocked will be excessive. He may usecore-spun yarns consisting of stretchable core yarns and sheathes ofstaple fibers, in which case his product will have a good hand and thenumber of sizes that must be stocked will be held to a minimum. However,as pointed out hereinabove, such yarns are not mercerized, and,therefore, the product will lack luster.

Accordingly, an important object of this invention is to provide amethod and apparatus for commercially mercerizing core-spun yarnsconsisting of stretchable core yarns and sheathes of staple fibers.

Another object is to provide such a method and apparatus wherein theyarns are not processed in the form of warps, but individually in smallnumbers, and tension in the individual yarns is maintained at a constanthigh level while the yarns are passing through the mercerizing solution.

Another object is to provide such a method and apparatus wherein theindividual yarn end mercerizing is effected at a comparatively high rateof speed and the lengths of the several individual yarn ends in thetension zone are simultaneously subjected each to a substantiallyuniform predetermined high percentage of of core-spun yarn 16. The yarnpasses from the cone 14 horizontally to a roll 21 and then at least onceabout the roll 21. From the roll 21 the yarn passes horizontally over aguide roll 22," downwardly and under a guide roll 23, upwardly and overa guide roll 24, downwardly and under. a guide 25, upwardly and over aguide roll 26, downwardly and under a guide roll 27, upwardly and over aguide roll 28, downwardly and under a guide roll 29, and upwardlyv andthrough the nip of a pair of rolls 30. It then passes preferably atleast once about one of the rolls 30 and then again throughthe nip ofthe rolls 30. From the nip of the rolls 30 the yarn passes horizontallythrough an electric or other heater 31, from whence it passes to and iswound into a cone 32 turned by a winder roll33. The rolls 23, 24 and 25are disposed in a compartment A of a tank 34, and the rolls 27, 28 and29 are disposed in a separate compartment B of the tank 34. Thecompartment A contains a mercerizing solution 36, and the compartment Bcontains a neutralizing solution 38. The tank 34 is mounted for beinglowered, as shown in brokenlines, to facilitate the operation ofthreading up the apparatus. The rolls 21 through 30 are fixed inposition. The rolls 21 through 29 idle while the rolls 30 are driven.The rolls 30 pull the yarn from the cone 14 against a drag induced byconventional means applied to the roll 21, as, for example, a weight 39.Stop motion means (not shown) may be provided to terminate operation ofthe apparatus in the eventthat the thread breaks.

In theoperation of the apparatus, the yarn is drawn from the cone 14 andthrough the mercerizing solution 36 and the neutralizing solution 38 bythe rolls 30. The grip of the rolls 30 on the yarn is firm enough toprevent slippage between the yarn and the rolls, without being greatenough to crush or otherwise injure the yarn. The yarn is drawn throughthe heater 31 by the cone 32 actuated by the winder roll 33. At thepresent time, yarn is processed by conventional apparatus at the rate ofapproximately twenty-five yards per minute, but yarn 16 preferably isprocessed in the order of 150 to 375 yards per minute.

When the yarn is wetted, it tends to shrink. However, in order to do so,the yarn must overcome the influence of the drag on the roll 21 inducedby the weight 39, in consequence of which the yarn is tensioned to alevel depending upon the weight 39, which is selected to produce aconstant tension which preferably is approximately 80 percent of thatwhich the yarn is able to withstand without breaking.

The arrangement of the rolls 22 through 26 is such that each successivelength of yarn preferably is immersed in the mercerizing solution 36 forabout ninety seconds. The mercerizing solution is conventional (a 25percent solution of sodium hydroxide plus agents to wet out the yarn)and, is maintained at room temperature. The arrangement of the rolls 26through 30 is such that each successive length of yarn is immersed inthe solution 38 for a period of time sufiicient for neutralizing thesolution 36 which the yarn picked up while passing through thecompartment A. The neutralizing solution 38 may be acid, but water mightbe used.

After the yarn passes through the nip of the rolls 30, it passes throughthe heater 31. The temperature of the heater must not be high enough toinjure the material, and the yarn must not be subjected to the heat foran excessive period of time. Preferably, when the yarn 4 leaves theheater, its moisture content should be at least equal to its moistureregain, and its pH should be approximately what it was before it enteredthe mercerizing solution 36.

If desired, the tank 34 may be provided with several additionalcompartments, and the, yarn ends may be passed successively through thetreatment solutions in the several compartments. For example, there maybe a treatment solution for tinting the yarn ends for identification, atreatment solution for dyeing, and a liquid for a resin treatment.

Although, as illustrated, one yarn end is processed at a time, it willbe understood that in practice my individual yarn end mercerizing mayinvolve simultaneously processing many yarn ends. In this event, a roll21 may be provided for each yarn end, and a drag inducing device may beprovided for each roll 21. Thus while the several yarn ends 16 are drawnfrom cones 14 by the rolls 30, each yarn end is tensionedindependentlyof the others by reason of the drag on the associated roll 21 workingagainst the yarn drawing effort of the rolls 30. Thus tension in theseveral yarn ends is maintained uniform and at the desired level.

The stretchable core yarn may be any filamentary yarn, natural orsynthetic, which is stretchable to some appreciable degree. The coreyarn may be a filamentary elastometric yarn, such as rubber or spandex(Lycra by E. I. du Pont de Nemours & Co., and Vyrene by US. Rubber Co.).It may be a bulk yarn of the crimp type, such as Textralized or Banlon.It may be a stretch yarn of the conventional type, such as Helanca, orof the false twist type, such as Superloft or Flufion, or of thenontorque type, such as Agilon. The staple fibers may be of any naturalor synthetic material.

In the event of a break in the yarn, the stop motion acts to terminateoperation. The tank is lowered, as shown in broken lines, the machinerethreaded and the tank raised again. If the core yarn is not spandex,no appreciable loss will occur due to overexposure to the mercerizingsolution. If the core yarn is spandex, the loss will be negligible.

It will be understood, of course, that the method and apparatushereinabove described is susceptible to various changes andmodifications which may be made without any departure from the generalprinciples or real spirit of the invention. For example, the positionsof the rolls 26 and 30 may be reversed because while it is essentialthat the yarn be tensioned during its passage through the mercerizingsolution 36, it is not necessary for it to be tensioned during itspassage through the neutralizing solution 38.

What is claimed is:

1. A continuous method of mercerizing stretchable composite yarncomprising a continuous-filament elastomeric core having staple fibersthereabout, said method comprising the steps of:

(a) continuously drawing the composite yarn from a source through amercerizing solution at a rate of at least 100 yards per minute tomaintain the composite yarn immersed in the mercerizing solution for theorder of ninety seconds;

(b) maintaining a constant drag of such magnitude on the yarn at a pointupstream of the mercerizing so lution that the yarn in the mercerizingsolution is stretched to the order of of its capacity;

(0) continuously drawing the mercerized composite yarn through aneutralizing solution;

(d) continuously drying the yarn, and then (e) packaging the yarn.

2. The method according to claim 1 characterized in that the mercerizedneutralized composite yarn is continuously dried by drawing the yarnthrough heater means.

3. The method according to claim 1 characterized in that the compositeyarn is drawn through the merceriz- 6 ing solution at a rate of theorder of 150375 yards per References Cited minute. NI ED TAT ATEN 4. Themethod according to claim 3 characterized in U T S ES P TS that themercerizing solution is a 25% solution of sodium 3334482 8/1967 Neel 2876 hydroxide plus wetting agents.

5. The method according to claim 4 characterized in 5 JOHN DAVID WALSHPnmary Exmamer that the mercerizing solution is at room temperature. USCl. XIR

6. The method according to claim 5 characterized in that the elastomericcore is spandex.

